The incidence of obesity is increasing dramatically in virtually all societies throughout the world. Further, accumulation of visceral fat, predominantly as white adipose tissue, in the abdominal regions is coincident with an elevated risk of developing type 2 diabetes, cardiovascular disease, and increased morbidity. The dominant cellular basis of obesity is increased fat cell (adipocyte) size and number and marked by accretion of triglycerides within intracellular lipid droplets. Adipocyte maturation is largely driven by the hormonal induction of nuclear receptors (NR);however, little is known about the specific, early pathways that complement NR activity and subsequent lipid accumulation in human cells. Recent studies have shown that the pi 60 NR coregulators (SRC-1, SRC-2, SRC-3) are requisite to coordinate a circuit of interacting transcription factors to drive adipogenesis. Genetic ablation of these coregulators (CoR) leads to obesity (SRC-1) and a reduction in white adipose deposition (SRC-3, SRC-2). Additionally, SRC-1/SRC-3 double knockout mice exhibit a lean phenotype. Structurally, the pi 60s share sequence homology within the six domains responsible for NR and transcription factor interactions. Biochemical studies have linked the pi 60s to peroxisome proliferator-activated receptor-gamma (PPAR), the master regulator of adipogenesis. These clues suggest the potential for a functional overlap between the pi 60s and a temporal element that drives their crosstalk with PPAR to promote adipogenesis. Therefore, I hypothesize that the pi 60s have redundant roles during the human adipogenic program. In this study, I propose the following aims to quantitatively index the role and functional overlap of the pi 60s during the early phases of human adipogenesis. Aim 1 will establish the spatiotemporal localization and expression levels occurring throughout the early phases of adipogenesis for SRC-1, SRC-2, and SRC-3. Aim 2 will determine the functional redundancy of SRC-1, SRC-2, and SRC-3 during human adipogenesis. A combinatorial siRNA and high throughput microscopy method will be applied to quantitatively index the adipogenic additivity, synergy, or antagonism between these pi 60 coregulators during differentiation. The objective of this fellowship is to obtain a more complete understanding of the roles and coordination of the pi 60s during human adipogenesis in a single cell framework using high throughput microscopy (HTM) and image analysis. PUBLIC HEALTH RELEVANCE: This approach allows for a rapid, parallel interrogation of hormone action leading to a more complete understanding of the mechanisms regulating human adipocyte differentiation. The findings will provide new intervention strategies to prevent the onset of obesity and the associated clinical outcomes.